The human eye has three types of cone cells, each sensitive to different ranges of wavelengths corresponding to red, green, and blue light. Assuming each cone can detect about 100 different shades, we can estimate the total number of colors visible to a human by multiplying the number of shades each cone can detect.
So, the calculation would be:
100 (shades from the first cone) × 100 (shades from the second cone) × 100 (shades from the third cone) = 1,000,000
Therefore, the answer is:
1,000,000